[PATCH] drm/qxl: Fix missing free_irq

[liwei (GF)]

On 2022/11/9 0:06, Daniel Vetter wrote:
> On Tue, Nov 08, 2022 at 11:16:01PM +0800, Wei Li wrote:
>> When doing "cat /proc/interrupts" after qxl.ko is unloaded, an oops occurs:
>>
>> BUG: unable to handle page fault for address: ffffffffc0274769
>> PGD 2a0d067 P4D 2a0d067 PUD 2a0f067 PMD 103f39067 PTE 0
>> Oops: 0000 [#1] PREEMPT SMP PTI
>> CPU: 6 PID: 246 Comm: cat Not tainted 6.1.0-rc2 #24
>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014
>> RIP: 0010:string_nocheck+0x34/0x50
>> Code: 66 85 c0 74 3c 83 e8 01 4c 8d 5c 07 01 31 c0 eb 19 49 39 fa 76 03 44 88 07 48 83 c7
>> RSP: 0018:ffffc90000893bb8 EFLAGS: 00010046
>> RAX: 0000000000000000 RBX: ffffc90000893c50 RCX: ffff0a00ffffff04
>> RDX: ffffffffc0274769 RSI: ffff888102812000 RDI: ffff88810281133e
>> RBP: ffff888102812000 R08: ffffffff823fa5e6 R09: 0000000000000007
>> R10: ffff888102812000 R11: ffff88820281133d R12: ffffffffc0274769
>> R13: ffff0a00ffffff04 R14: 0000000000000cc4 R15: ffffffff823276b4
>> FS:  000000000214f8c0(0000) GS:ffff88842fd80000(0000) knlGS:0000000000000000
>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> CR2: ffffffffc0274769 CR3: 00000001025c4005 CR4: 0000000000770ee0
>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>> PKRU: 55555554
>> Call Trace:
>>  <TASK>
>>  string+0x46/0x60
>>  vsnprintf+0x27a/0x4f0
>>  seq_vprintf+0x34/0x50
>>  seq_printf+0x53/0x70
>>  ? seq_read_iter+0x365/0x450
>>  show_interrupts+0x259/0x330
>>  seq_read_iter+0x2a3/0x450
>>  proc_reg_read_iter+0x47/0x70
>>  generic_file_splice_read+0x94/0x160
>>  splice_direct_to_actor+0xb0/0x230
>>  ? do_splice_direct+0xd0/0xd0
>>  do_splice_direct+0x8b/0xd0
>>  do_sendfile+0x345/0x4f0
>>  __x64_sys_sendfile64+0xa1/0xc0
>>  do_syscall_64+0x38/0x90
>>  entry_SYSCALL_64_after_hwframe+0x63/0xcd
>> RIP: 0033:0x4bb0ce
>> Code: c3 0f 1f 00 4c 89 d2 4c 89 c6 e9 bd fd ff ff 0f 1f 44 00 00 31 c0 c3 0f 1f 44 00 00
>> RSP: 002b:00007ffd99dc3fb8 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
>> RAX: ffffffffffffffda RBX: 0000000001000000 RCX: 00000000004bb0ce
>> RDX: 0000000000000000 RSI: 0000000000000003 RDI: 0000000000000001
>> RBP: 0000000000000001 R08: 000000000068f240 R09: 0000000001000000
>> R10: 0000000001000000 R11: 0000000000000246 R12: 0000000000000003
>> R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000000
>>  </TASK>
>>
>> It seems that qxl doesn't free the interrupt it requests during unload,
>> fix this by adding the missing free_irq().
>>
>> Fixes: f64122c1f6ad ("drm: add new QXL driver. (v1.4)")
>> Signed-off-by: Wei Li <liwei391 at huawei.com>
> 
> Could we go right ahead and switch over to devm_request_irq? Or does that
> not quite do the right thing here?


I tried to use devm_request_irq() to free the irq automatically, but find lots of memory
leak reported by qxl_bo_fini() when CONFIG_DRM_DEBUG_MM=y.

I found that qxl_io_notify_oom() in qxl_device_fini() trigerred an interrupt with
QXL_INTERRUPT_DISPLAY pending and then queued a garbage collect, while devm_irq_release()
is called before drm_dev_release(), if we use devm_request_irq() then we will miss
the interrupt.

So i choose to free irq here, should we enforce a garbage collect here to fix this? then we
can just use devm_request_irq.

Thanks,
Wei

>> ---
>>  drivers/gpu/drm/qxl/qxl_kms.c | 3 +++
>>  1 file changed, 3 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/qxl/qxl_kms.c b/drivers/gpu/drm/qxl/qxl_kms.c
>> index dc3828db1991..d591084824de 100644
>> --- a/drivers/gpu/drm/qxl/qxl_kms.c
>> +++ b/drivers/gpu/drm/qxl/qxl_kms.c
>> @@ -283,6 +283,8 @@ int qxl_device_init(struct qxl_device *qdev,
>>  void qxl_device_fini(struct qxl_device *qdev)
>>  {
>>  	int cur_idx;
>> +	struct drm_device *ddev = &qdev->ddev;
>> +	struct pci_dev *pdev = to_pci_dev(ddev->dev);
>>  
>>  	/* check if qxl_device_init() was successful (gc_work is initialized last) */
>>  	if (!qdev->gc_work.func)
>> @@ -305,6 +307,7 @@ void qxl_device_fini(struct qxl_device *qdev)
>>  	wait_event_timeout(qdev->release_event,
>>  			   atomic_read(&qdev->release_count) == 0,
>>  			   HZ);
>> +	free_irq(pdev->irq, ddev);
>>  	flush_work(&qdev->gc_work);
>>  	qxl_surf_evict(qdev);
>>  	qxl_vram_evict(qdev);
>> -- 
>> 2.25.1
>>
>